Implement Delegate Property Validation with Generics

krate/src/main/kotlin/hu/autsoft/krate/Functions.kt

@@ -14,7 +14,7 @@ import hu.autsoft.krate.optional.IntDelegate
 import hu.autsoft.krate.optional.LongDelegate
 import hu.autsoft.krate.optional.StringDelegate
 import hu.autsoft.krate.optional.StringSetDelegate
-import hu.autsoft.krate.validated.optional.ValidatedStringDelegate
+import hu.autsoft.krate.validated.ValidatedPreferenceDelegate
 import kotlin.properties.ReadWriteProperty
 
 /**
@@ -65,7 +65,7 @@ public fun Krate.stringPref(key: String): ReadWriteProperty<Krate, String?> {
  * @return [ReadWriteProperty]
  */
 public fun Krate.stringPref(key: String, isValid: (String?) -> Boolean): ReadWriteProperty<Krate, String?> {
-    return ValidatedStringDelegate(StringDelegate(key), isValid)
+    return ValidatedPreferenceDelegate(StringDelegate(key), isValid)
 }
 
 /**

krate/src/main/kotlin/hu/autsoft/krate/optional/StringDelegate.kt

@@ -1,7 +1,6 @@
 package hu.autsoft.krate.optional
 
 import hu.autsoft.krate.Krate
-import hu.autsoft.krate.validated.exception.KrateValidationException
 import hu.autsoft.krate.util.edit
 import kotlin.properties.ReadWriteProperty
 import kotlin.reflect.KProperty

krate/src/main/kotlin/hu/autsoft/krate/validated/ValidatedPreferenceDelegate.kt

@@ -0,0 +1,28 @@
+package hu.autsoft.krate.validated
+
+import hu.autsoft.krate.Krate
+import hu.autsoft.krate.validated.exception.KrateValidationException
+import kotlin.properties.ReadWriteProperty
+import kotlin.reflect.KProperty
+
+/**
+ * [ValidatedPreferenceDelegate] is a generic [ReadWriteProperty] that can be used to
+ * validate values that are being set.
+ *
+ * @param [delegate] the [ReadWriteProperty] implementation that is used for delegation
+ * @param [isValid] the lambda used to validate property values on [setValue]
+ */
+internal class ValidatedPreferenceDelegate<T>(
+        private val delegate: ReadWriteProperty<Krate, T>,
+        private val isValid: (T) -> Boolean
+) : ReadWriteProperty<Krate, T> by delegate {
+
+    override operator fun setValue(thisRef: Krate, property: KProperty<*>, value: T) {
+        if (!isValid(value)) {
+            throw KrateValidationException("$value is not valid.")
+        }
+
+        delegate.setValue(thisRef, property, value)
+    }
+
+}